1. Field of the Invention
This invention relates to water soluble enamel compositions. More particularly, it relates to water soluble wire enamels which have high thermal stability.
2. Description of the Prior Art
A large percentage of the wire enamels commercially produced today are solvent-based systems, utilizing such solvents as cresylic acids, xylene, and other hydrocarbons. Examples of these types of enamels are shown in U.S. Pat. No. 3,555,113. During the wire coating process these solvents are not recovered and must be incinerated to meet pollution regulations. This is generally accomplished by mounting flame burners on the top of the enameling equipment, which involves considerable extra expense resulting from maintenance and operation of the incinerators and total loss of solvent.
These problems make water soluble wire enamels very attractive since they offer no pollution problems and avoid the associated expenses. However, until now a major drawback of water soluble enamels has been their low thermal ratings. The only water soluble wire enamels available today are not polyester enamels and only have Class A (105.degree. C.) thermal ratings. This is insufficient for many wire coating applications which require greater thermal stability at higher temperatures.
Accordingly, it is an object of the invention to develop a water soluble wire enamel having a Class F (155.degree. C.) thermal rating. This and other objects will become apparent upon further reading of the specification.